Make helper functions static. NFC.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@304029 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/AMDGPU/GCNRegPressure.cpp b/lib/Target/AMDGPU/GCNRegPressure.cpp
index 18374dc..390a828 100644
--- a/lib/Target/AMDGPU/GCNRegPressure.cpp
+++ b/lib/Target/AMDGPU/GCNRegPressure.cpp
@@ -211,9 +211,9 @@
   return getLiveLaneMask(MO.getReg(), SI, LIS, MRI);
 }
 
-SmallVector<RegisterMaskPair, 8> collectVirtualRegUses(const MachineInstr &MI,
-                                              const LiveIntervals &LIS,
-                                              const MachineRegisterInfo &MRI) {
+static SmallVector<RegisterMaskPair, 8>
+collectVirtualRegUses(const MachineInstr &MI, const LiveIntervals &LIS,
+                      const MachineRegisterInfo &MRI) {
   SmallVector<RegisterMaskPair, 8> Res;
   for (const auto &MO : MI.operands()) {
     if (!MO.isReg() || !TargetRegisterInfo::isVirtualRegister(MO.getReg()))